1. Field of the Invention
This invention relates to power supply regulation and, more particularly, to the regulation of power supplied to sensitive analog circuitry.
2. Description of the Related Art
High performance wireless communication apparatus such as RF receivers, transmitters, and transceivers typically include RF front-end circuitry that operates on an RF signal being received or transmitted. For example, the front-end circuitry may down-convert a received RF signal to base band and/or up-convert a base band signal for RF transmission.
The RF front-end circuitry typically includes analog circuits such as low noise amplifiers and mixers that have a relatively high sensitivity to noise and interference. The RF circuitry in some applications, such as in mobile communication cellular handsets, may be required to detect signals as small as a few micro-volts or less in amplitude. It is thus often important to minimize noise and interference from sources external or even internal to the communication apparatus.
One source of noise that may adversely affect operation of the RF front-end circuitry is power supply noise. Power supply noise can originate from noisy digital circuits internal to an integrated circuit chip or can come from components such as battery or regulators external to the chip. Power supply noise may be a particular problem, for example, in systems that also include digital circuitry (such as digital base band circuitry), since significant amounts of noise may be induced at the power supply node due to clocking of the digital circuitry.
To reduce the adverse affects of power supply noise on the sensitive analog circuitry, some communication apparatus therefore employ linear regulator circuits to regulate the power provided from the power supply to the analog circuitry. While this arrangement may greatly improve the negative effects of power supply noise on the operation of the analog circuitry, unfortunately, the linear regulator circuit may consume relatively large amounts of power. In the designs of many systems and particularly in battery powered systems, it is a significant goal and challenge to minimize power consumption.